New Zealand has lost its first female soldier since the Vietnam war in a roadside bomb attack in Afghanistan which claimed three lives.

Medic Lance Corporal Jacinda Baker, 26 of Christchurch, Corporal Luke Tamatea, 31, of Kawerau, and Richard Harris, 21, of Pukekohe died helping a fellow soldier about 9.20am Afghanistan time (5pm NZ time) yesterday when their humvee was hit by a roadside bomb in Bamiyan province. Their vehicle was the last in a convoy taking one of their patrol members to Romero base to see a doctor.

A second bomb was found and disarmed, while the remaining personnel in the patrol secured the location and awaited more support.

The attack occurred northwest of Do Abe, near where Lance Corporals Rory Malone and Pralli Durrer were killed in a firefight only two weeks ago.

Defence Force Chief Lieutenant General Rhys Jones said Baker was the first female killed in action since the Vietnam war when a nurse was killed. Females were also killed in World War 2.

There were 10 women serving in Bamiyan and another two at the United States air base at Bagram near the capital Kabul, he said. Women made up 16 per cent of the wider Defence Force.

New Zealand wasn't unique having women on the front line, Jones said. "A lot of European countries are putting women on the front line because of the roles we do with community engagement. Having women there to interact with children and other women in Islamic society becomes quite important."

Baker went to the Solomons Islands in 2010. She received a chief of army commendation in 2011 for her professionalism and courage. She had a partner in the army.

The humvee was being driven by Harris who joined the army in 2009 and was previously deployed to Timor-Leste.

Tamatea joined the army in 2000 and served in Timor Leste in 2001, the Solomons 2003 and helped with the tsunami recovery in Sumatra in 2005. He had previously served in Afghanistan in 2007.

All three soldiers were deployed to Bamiyan in April and were from the 2nd/1st battalion royal infantry.

Their bodies were evacuated by helicopter and an Australian military aircraft would take them back to Australia from where they would be flown home.

Casualties were possible at any time in Afghanistan, Jones said.

"The group that we are operating against is very proficient and we know they have other IEDs (improvised explosive devices)."

The Defence Force was aware of the psychological impact of the recent deaths on troops in Bamiyan and a specialist team was now in the province helping the contingent, he said.

Prime Minister John Key told a press conference, which was also attended by Jones and Defence Minister Jonathan Coleman, that the soldiers' sacrifice would not be forgotten.

Ministers had for some weeks been considering options for an "orderly withdrawal".

A decision was still to be finalised but it was likely to take place in the earlier part of 2013, Key confirmed.

"There is no question we are coming home."

New Zealand had to withdraw in conjunction with its international partners, he said.

"Otherwise the signal we send to the rest of the whole of Afghanistan is that it's time to run for the exit. If you do that then the thousands of people who have lost their lives have been in vain."

Key conceded keeping troops in the war-torn nation was a hard call.

"Every time I get a phone call from the Defence Minister or the Chief of the Defence Force about this, it is a gut-wrenching experience. I want our boys and girls to come home."

The timing of the withdrawal had not been affected by loss of five soldiers in last few weeks, he said. New Zealand has now lost 10 soldiers in Afghanistan.

Coleman said it was "absolutely gutting" to be delivering such news again so soon after last week's funerals for Malone and Durrer.

"This is the most terrible day that could ever be visited on loved ones of a service person."

KEY: WE DON'T CUT AND RUN

It would take months, not days, for New Zealand to withdraw, Key said.

"We made a commitment... I don't think we are the type of country that cuts and runs."

There were three large New Zealand bases with about 150 troops and the soldiers were supporting New Zealand aid workers in the province.

Key said the three troops were killed instantly as a result of an "enormous explosion" from a road-side bomb.

A LAV would have been carrying seven troops, so more people could have been killed if they were not in the humvees, Key said.

The blast was attributed to bomb makers who were part of a new insurgent group the New Zealanders had been targeting.

Key said he was confident the soldiers had the equipment they needed but he would be double-checking with the Defence Force today.

Replacement troops had arrived in Afghanistan following Durrer and Malone's deaths. They were specialist troops, due to the bomb-making threat.

Jones said the Kiwis had been working for some time to disrupt the bombmakers.

He believed the "bombmaker" forces had been trying to track was still out there.

Labour Foreign Affairs spokesman Phil Goff, a former defence minister, said it was not a case of "cutting and running".

"It's a case of managing an orderly transition out of Bamiyan which the Government should have been embarking on already."

New Zealand had done everything it could in the province.

"There is nothing further we can do to influence outcomes in Bamiyan or in Afghanistan. To justify sacrifice, you've got to have obtainable objectives.

"Things are going backwards in Afghanistan, not forwards. Not because of what our guys are doing but because the [Afghanistan] government has failed utterly to win the support of its own people."

There has been a string of attacks in Afghanistan this weekend, including the shooting of an international service member by a man in Afghan police uniform.

CONDOLENCES OFFERED

Among the many to offer their condolences, Key, Jones and Coleman were joined by Governor-general Sir Jerry Mateparae, a former Defence Force chief, and the RSA.

All said they were deeply saddened and that their thoughts were with the victims' families.

DEATHS PROMPTED EXTENDED ROLE

Cabinet approved New Zealand's Bamiyan-based Defence Force staff extending operations east into the hostile Baghlan province following the firefight which killed Malone and Durrer and injured six other Kiwi soldiers.

Durrer and Malone, both 26, were on their first deployment to Afghanistan as part of the Provincial Reconstruction Team (PRT). The insurgents which killed them were from Baghlan province.

Baghlan is the responsibility of Hungarian forces, who are reluctant to patrol the area, however, Key has ruled out seeking a change to the Hungarian's rules of engagement.

The reluctance of the Hungarians to patrol their area had led to an increase in insurgent activity in recent years, Key said.

"It's a very hostile environment and it's a dangerous and difficult environment there."